A key fact about online [and offline] communities is that the people who participate the most eventually influence the direction and culture of the community. Kuro5hin tried to fix two problems with Slashdot, the lack of a democratic voting system and the focus on mindless link propagation instead of deeper, more analytical articles. I mentioned how this experiment ended up in my post Jeff linked to which is excerpted below

Now five years later, I still read Slashdot every day but only check K5 out every couple of months out of morbid curiosity. The democracy of K5 caused two things to happen that tended to drive away the original audience. The first was that the focus of the site ended up not being about technology mainly because it is harder for people to write technology articles than write about everyday topics that are nearer and dearer to their hearts. Another was that there was a steady influx of malicious users who eventually drove away a significant proportion of K5's original community, many of whom migrated to HuSi. This issue is lamented all the time on K5 in comments such as an exercise for rusty and the editors. and You don't understand the nature of what happened.

Besides the malicious users one of the other interesting problems we had on K5 was that the number of people who actually did things like rate comments was very small relative to the number of users on the site. Anytime proposals came up for ways to fix these issues, there would often be someone who disregarded the idea by stating that we were "seeking a technical solution to a social problem". This interaction between technology and social behavior was the first time I really thought about social software.

The common theme underscoring both problems that hit the site is that they are all due to the cost of participation. It is easier to participate if you are writing about politics during an election year than if you have to write some technical article about the feasibility of adding garbage collection to C++ or analysis of distributed computing technologies. So users followed the path of least resistance. Similarly, cliques of malicious users and trolls have lots of time on their hands by definition and Kuro5hin never found a good way to blunt their influence. Slashdot's system of strong editorial control and meta-moderation of comment ratings actually turned out to be strengths compared to kuro5hin's more democratic and libertarian approach.

A funny thing about these sites is that they know about this problem. Hacker News is very concerned about not turning into the next Reddit; Reddit was created as a better Digg; and Digg's corporate mission statement is "at least we're not Slashdot." None of them seem to realize that the order from least to most horrible is identical to the order from youngest to oldest, or that every one of them was good once and isn't any longer. ...When you build a system where you get points for the number of people who agree with you, you are building a popularity contest for ideas. However, your popularity contest for ideas will not be dominated by the people with the best ideas, but the people with the most time to spend on your web site. Votes appear to be free, like contribution is with Wikipedia, but in reality you have to register to vote, and you have to be there frequently for your votes to make much difference. So the votes aren't really free - they cost time. If you do the math, it's actually quite obvious that if your popularity contest for ideas inherently, by its structure, favors people who waste their own time, then your contest will produce winners which are actually losers. The most popular ideas will not be the best ideas, since the people who have the best ideas, and the ability to recognize them, also have better things to do and better places to be.

Even if you didn't know about the long tail, you'd look for the best ideas on Hacker News (for example) not in its top 10 but in its bottom 1000, because any reasonable person would expect this effect - that people who waste their own time have, in effect, more votes than people who value it - to elevate bad but popular ideas and irretrievably sink independent thinking. And you would be right. TechCrunch is frequently in HN's top ten.

I agree with everything excerpted above except for the implication that all of these sites want to be "better" than their predecessors. I believe that Digg simply wants to be more popular (i.e. garner more page views) than its predecessors and competitors. If the goal of a site is to generate page views then a there is nothing wrong with a popularity contest. However the most popular ideas are hardly ever the best ideas, they are often simply the most palatable to the target audience.

As a user, being popular in such online communities requires two things; being prolific and knowing your audience. If you know your audience, it isn't hard to always generate ideas that will be popular with them. And once you start generating content on a regular basis, you eventually become an authority. This is what happened with MrBabyMan of Digg (and all the other Top Diggers) who has submitted thousands of articles to the site and voted on tens of thousands of articles. This is also what happened with Signal 11 of Slashdot almost a decade ago (damn, I'm getting old). In both the case of MrBabyMan (plus other Top Diggers) and Signal 11, some segment of the user base eventually cottoned on to the fact that participation in a social news site is a game and rallied against the users who are "winning" the game. Similarly in both cases, the managers of the community tried to blunt the rewards of being a high scorer - in Slashdot's case it was with the institution of the karma cap while Digg did it by getting rid of the list of top Diggers.

Although turning participation in your online community into a game complete with points and a high score table is a good tactic to gain an initial set of active users, it does not lead to a healthy or diverse community in the long run. Digg and Slashdot both eventually learned this and have attempted to fix it in their own ways.

Social news sites like Reddit & Digg also have to contend with the fact that the broader their audience gets the less controversial and original their content will be since the goal of such sites is to publish the most broadly popular content on the front page. Additionally, ideas that foster group think will gain in popularity as the culture and audience of the site congeals. Once that occurs, two things will often happen to the site (i) growth will flatten out since there is now a set audience and culture for the site and (ii) the original crop of active users will long for the old days and gripe a lot about how things have changed. This has happened to Slashdot, Kuro5hin, Reddit and every other online community I've watched over time.